The decline in glucose tolerance with age has been amply confirmed. The definition of levels of performance which should be considered abnormal at different ages remains in doubt. The mechanism of the decline is also under study. The relation of obesity to glucose intolerance is known. The effect of changes in obesity with aging on glucose homeostasis is under study. The possibility of a racial (i.e., genetic) factor in a high prevalence population (Pima Indians) is being investigated. In addition, characterization of subjects by their hemoglobin Alc levels is being explored since this value gives an index of the integrated blood glucose concentration over a period of months.